As installing git and MacPorts on my MAC wasn’t as simple as I thougt before, here are the necessary steps to get MacPorts and git on your Leopard:
Install Xcode 3.0, which can be found on your Mac OS Setup CD, or here.
Install X11, which you can also find on the OS X Setup CD
Download and Install MacPorts
Update your ~/.profile:
Install git via MacPorts:
sudo port install git-core
A more comprehensive guide on installing MacPorts can be found here.